Recently, studies on compounds exhibiting inhibitory activity against cyclic GMP phosphodiesterase (hereinafter referred to as "cGMP-PDE") have proceeded and attempts have been made to apply such compounds to the prevention and treatment of circulatory failures such as hypertension, angina pectoris and myocardial infarct.
Known examples of the compound usable in the prevention and treatment of circulatory failures include quinazoline compounds disclosed in JP-A-29582/1975, 4H-3,1-benzoxazin-4-one compounds disclosed in WO 88/09790, 1H-2,3,4,5-tetra-hydroimidazo[2,1-b)quinazolin-2-one and 1,2,3,4,5,6-hexahydropyrimido[2,1-b]quinazolin-2-one disclosed in JP-A-86894/1973, nitrogenous heterocyclic compounds disclosed in WO 93/07124 and 4-aminoquinazoline derivatives disclosed in EP 579496.
However, most of the compounds described above are not on the market and many of them have problems of solubility, in vivo dynamics and toxicity which must be solved prior to the use as drugs.